Many smartphones and other battery-powered mobile devices are designed around hierarchical architectures in which a primary hardware unit that executes the operation system, apps, and other programs is supported by a number of “peripheral subsystems”—separate hardware resources that each provide specialized services, such as a cellular modem that encodes and decodes data for transmission via a cellular wireless network; a GPS subsystem that determines the geographic location of the device; a video subsystem that controls the display; a camera subsystem for capturing images; a wi-fi subsystem that interacts with other devices via a wi-fi or Bluetooth connection; etc. In many cases, the primary hardware unit is implemented as a System on a Chip (“SoC”), as are one or more of the peripheral subsystems. Each SoC generally has one or more processing cores (e.g., microprocessors, microcontrollers, or digital signal processors), a timing source, memory, and a bus. SoCs and other hardware arrangements implementing peripheral subsystems often also contain specialized hardware resources, such as radios, wired interfaces, electronic compasses, etc.
As part of its operation, each peripheral subsystem (hereafter simply “subsystem”) may crash. The operating system executing on the main processor often has multiple ways of learning that a particular subsystem has crashed, such as being explicitly notified by the subsystem, being implicitly notified by the subsystem, or determining that the subsystem has not reset a watchdog timer on schedule. Conventionally, when the operating system learns that a particular subsystem has crashed, it first collects “telemetry data” for the crash (also called “diagnostic data”)—status information that may help explain the reason for the crash, such as a “fatal error string” that seeks to describe the nature of the crash textually. The operating system then makes the telemetry data available for analysis, such as by sending the telemetry data to an analysis service such as the Windows Error Reporting service. As part of making the telemetry data available for analysis, the operating system reboots the main processor. The rebooting process restarts the device's subsystems, including the crashed subsystem. At the conclusion of this process, the crashed subsystem's normal functioning in support of the main processor generally resumes.